The invention relates to a method for regenerating an adsorber or absorber on board a submarine.
Submarines are generally equipped with solid or liquid adsorbers or absorbers in order to bind harmful gases from the cabin air. Harmful gases in this case can be metabolic products given off by people to the cabin air, outgassing products of materials and processes, and also leaks from units.
In the case of the metabolic products, the binding of expired CO2 is of most importance quantitatively. In addition, numerous volatile organic compounds (VOCs) are emitted not only by people but also by materials and processes.
Whereas for submarines having short submerge times, frequently non-reversible binding concepts are used such as, e.g., lithium hydroxide or soda lime for binding CO2 and activated carbon for binding VOCs, in the case of submarines that are submerged for relatively long periods such as nuclear-propelled submarines or air independent propulsion (AIP) submarines, regenerative binding methods are used. Because binder is thereby saved, the space requirement for storing the binder is decreased. This advantage, however, increases the energy requirement necessary for regeneration. In nuclear-propelled submarines, this is not usually a problem. In the case of AIP submarines, however, electrical energy for regenerating systems binding harmful gases is available only to a very limited degree.
Regenerative binding methods require electrical energy, e.g. for a fan, a gas compressor for transferring harmful gases outboard, or for control elements. Frequently, energy is also required for heating the ad/absorbents or for generating steam for the regeneration. This can be electrical energy or thermal energy.
Submarines having AIP drive designs, in which waste heat is produced at the required level and can be utilized, such as, e.g., in the case of submarines having a Stirling engine, closed diesel engine or reformer for fuel cells, are advantageous here for generating heat or steam.
In submarines having fuel cells and H2/O2 as fuel, customarily a reformer is not required and the waste heat of the fuel cell is at too low a level to be able to be used expediently. For such submarines, therefore, new designs are required in order that the requirement for thermal energy can be covered.
German Patent document DE 10 2006 048 716 B3 discloses a method in which H2 and O2, which are already present on board for operating the fuel cells, are burnt in order, utilizing the heat of the reaction, to generate steam from liquid water for the process of regenerating CO2 binding systems. A further variant also provides utilization of the steam resulting from the reaction of H2 and O2 for the regeneration. In this reaction, no further exhaust gas components such as, e.g., CO2 or CO are formed.
However, this known process requires large tanks to store the hydrogen. Usually, for this purpose, metal hydride stores are used in which the loading density is less than 3% by weight.
German Patent document DE 690 02 112 T2 and French Patent document FR 2 552 160 A1 each disclose thermal steam engines for use in a submarine in which the water used as working medium is converted into superheated steam from the combustion of a hydrocarbonaceous energy carrier with oxygen in a Stirling-Hirn cycle process. In German Patent document DE 690 02 112 T2, the CO2 formed in the combustion is stored in cylinders arranged on the outside of the stern of the submarine and which originally contained the oxygen required for the combustion. In French Patent document FR 2 552 160 A1, the CO2 formed is transferred outboard using a compressor.
It is therefore the object of the invention to provide a method for regenerating adsorbers/absorbers loaded with metabolic CO2 on board submarines, in which the storage volume of the energy carrier necessary for the regeneration can be considerably decreased.
According to the invention, for generating thermal energy, a hydrocarbonaceous, generally liquid, energy carrier is used such as, e.g., ethanol, methanol, propane, butane etc., for the combustion with O2.
The gases formed in the combustion of these energy carriers, in addition to steam, are transferred outboard according to the invention using a compressor. Since, for the regenerative CO2 binding system for removing the metabolic CO2, generally a CO2 compressor is already present on board, this compressor can advantageously also be used for transferring exhaust gases outboard.
In order to keep the amount of exhaust gas for the compressor as small as possible, an exhaust gas cooler with condensate separation can be connected upstream.
In principle, the thermal energy generated by the combustion can be used in two different ways for the regeneration:
1. The heat of combustion can be utilized for vaporizing water. The steam thus produced is utilized for regenerating the adsorbers or absorbers.
A special use thereof is regeneration processes, in which saturated or superheated steam between 80-150° C. is required for expelling the harmful gases from the adsorber, such as, e.g., in the regeneration of CO2 adsorbers based on solid amine or the regeneration of zeolite beds after the binding of metabolic CO2. Further suitable adsorbers are ion-exchange resins or solid amines for CO2 binding, in particular those described in German Patent document DE 198 30 470 C1 which is herein incorporated by reference. Furthermore, the adsorber can contain a zeolite for binding VOCs or a Freon, in particular R134a. All of the adsorbers mentioned here are also suitable for regeneration by energy input (see hereinafter 2).
Only the liquid water vaporized by the heat of combustion is used for the regeneration, whereas the combustion products (CO2, H2O and any further by-products) are conducted separately therefrom, bypassing adsorber and absorber, to the compressor, where they are disposed of outboard.
2. The heat of combustion can also be used directly, i.e. without intermediate connection of a water vaporization, for regenerating the adsorbers or absorbers. Here, in particular absorbers can be used in the form of a liquid amine, e.g. monoethanolamine MEA.
The invention has the advantage that the hydrocarbonaceous energy carriers are stored at a higher loading density and energy density, which results in a markedly lower storage volume than in the known H2/O2 combustion method.
The invention is suitable, in particular, for use in submarines having AIP drive designs, e.g. those based on fuel cells.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.